IMPROVED STAPLES

Abstract: A method and apparatus is provided for performing a stapling operation wherein uniform compression of stapled tissue is achieved. A staple (300) having two leg portions (302) and a crown (301) is used to staple tissue together. The staple legs comprise deformation zones (305) where the staple legs will bend during the stapling of tissue. The zones are located such that when deformed, the staple (300) forms a rectangular shape with rounded corners.

Description: IMPROVED STAPLES Technical Field » This invention relates to stapling and, more particularly, to improved staples for use in surgery and in other fields. Background of the Invention Staples have a variety of uses. For example, surgeons use thin wire staples to join the cut ends of hollow organs or ducts (anastomosis) and to achieve hemostasis. Thin wire staples are made by deforming a length of thin wire with uniform cross section and material properties to a U-shape. FIG. 1 shows a common prior art thin wire staple 100, including a crown 101 and two legs 102. The staple shown in FIG. 1 has uniform cross section and material properties, except as these may be altered in the region where the staple legs join the crown during deformation of the wire to the U- shape. Surgical staples are made of materials inert to attack by body fluids, e.g.; stainless steels. When a staple is installed, its legs are pushed into the material being stapled. During installation, some staples are deformed, i.e., bent past their elastic limit to achieve a permanent change in shape. FIG. 2 shows the staple of FIG. 1 deformed to a B-shape during installation due to its legs having been forced against an anvil with channels to direct the legs as they bend and deform. This anvil is located on the side of the material being stapled that is * opposite to the side into which staple insertion is made. The ^ deformation of the staple of FIG. 1 occurs where the maximum bending stress develops. FIG. 2 shows that the separation of different locations on the legs 102 from the crown 101 varies for a B-shaped staple. Thus, when B-shaped staples are used in surgery, tissues located between different regions of the legs and the crown undergo varying degrees of compression. To achieve hemostasis using staples, the tissue compressed least by the staples must still be compressed sufficiently for the hemostasis despite the possibility that the tissue compressed most may be perforated or damaged due to excessive compression br distortion. Shrinkage of scar tissue over time can lead to adverse results, and thus it is important to avoid forming more scar tissue than necessary. Despite the need to avoid excessive scar tissue, some surgeons claim that a controlled small amount of tissue damage can sometimes be beneficial provided that the amount of scar tissue formed as a result of the tissue damage is not excessive, i.e., so that the scar tissue formed does not cause the problems associated the excessive amounts of scar tissue resulting from use of prior art B-shaped staples. It is an object of the present invention to provide a staple which achieves uniform compression of stapled material. It is also an object of the present invention to provide a surgical staple which minimizes scar tissue formation. It is a further object of the present invention to provide a staple which minimizes distortion of the material stapled. It is an additional object of the present invention to provide a surgical staple which minimizes healing time. It is a further object of the present invention to provide a staple which minimizes damage of material stapled. It is a further object of the present invention to produce a staple for use in surgery which results in formation of a small controlled amount of scar tissue. Summary of the Invention The above cited problems and others are overcome and the objects of the invention are achieved in accordance with the invention which relates to an improved staple whose resistance to deformation during installation preferentially occurs in predetermined regions although in the absence of such weakening deformation would not otherwise preferentially occur in said predetermined regions. Such predetermined regions with weakened resistance to deformation are hereinafter termed "deformation zones". Deformation zones may be formed by reducing the minimum moment of inertia, I, of the staple cross section in the deformation zones, or by reducing the modulus or elasticity, E, of the staple material. In the preferred embodiment of the inventive staple, the staple has two legs, and each leg has a deformation zone in a predetermined region that is separated from the staple crown by a leg region with greater resistance to deformation than that of the deformation zone under the stress generated when the staple encounters an anvil during installation, so that the staple preferentially deforms in the deformation zone. During installation, the inventive staple is, preferably, deformed to a rectangular shape with rounded corners. This helps to achieve uniform compression and to minimize distortion of the stapled material. FIG. 1 depicts a prior art staple before installation; FIG. 2 shows the prior art staple of FIG. 1 after being deformed to a B-shape; FIG. 3 depicts an exemplary embodiment of the inventive staple; FIG. 4 shows the staple of FIG. 3 after being deformed to a rectangular shape; FIG. 5 shows exemplary cross sectional views (not to the scale of FIG. 3) of possible deformation zone and adjacent leg regions for the staple of FIG. 3; FIG. 6 shows a double staggered staple line; FIG. 7 is a partial front view in section of a first type of exemplary anvil; FIG. 8 is a partial front view in section of a second type of exemplary anvil; FIG. 9 is an alternative embodiment of the invention for use on material with varying thickness; FIG. 10 depicts a loaded strip (cartridge) of staples for use with the invention; FIG. 11 shows an alternative embodiment of the present invention wherein the deformation zones are formed simultaneously with the installation of the staples; FIG. 12 shows the embodiment of FIG. 11 in use; FIG. 13 shows a cross sectional view of the inventive staple fully deformed and installed into tissue; FIG. 14 shows an alternative embodiment of the inventive staple prior to deformation and installation; FIG. 15 shows a cross sectional view of a prior art staple fully deformed to a B-shape and installed into tissue; FIG. 16 shows a technique of forming deformation zones; and FIG. 17 shows a view of a notch formed on the outside of a staple leg. Detailed Description of the Preferred Embodiments A deformation zone is created by weakening the staple in a predetermined region so that deformation preferentially occurs in that region during staple installation. As is well-known in the art, the resistance to deformation of a region of a staple under stress is dependant on the magnitudes of its modulus of elasticity, E, in the region and the moment of inertia, I, in the region. Reducing one or both of these quantities in a region reduces the stress needed to deform a staple in that region. It is usually easier to reduce I than E. Deformation zones should not be formed by weakening the staple in the predetermined regions in such a manner as to result in staple failure, i.e., breakage, during staple deformation. The legs of the inventive staple should be matched to the requirements of the material stapled. That is, the locations of the deformation zones should be matched to the thickness of the material being stapled and to the compression desired, and the staple leg lengths should be sized to bring the legs into close proximity to achieve uniform compression of the stapled material and to prevent a bulge of material from between the tips of the legs. While such matching may require the availability of multiple staples, this is justifiable when the compression achieved and its uniformity are important. FIG. 3 shows an exemplary staple 300 in accordance with the present invention. The staple 300 includes a crown 301 and two legs 302. Each leg 302 has a deformation zone 305 with weakened resistance to bending into direction 304 as compared to the resistance of leg regions 306 and 307 which lie outside of the deformation zone 305. When the staple 300 is subjected to stresses arising from forces acting in the direction 304, the legs will bend into that direction, and bending and deformation will take place preferentially in deformation zone 305. In FIG. 4, the staple of FIG. 3 is shown deformed into a rectangular shape. Material stapled with the staple of FIG. 3 will be under more uniform compression than is the case with the B- shaped staple of FIG. 2. FIG. 4 reveals that the location and length of deformation zone 305 and the length of the staple leg 302 are important leg parameters in obtaining a desired compression for stapled material of a particular thickness and in bringing the staple leg ends into close proximity. Ideally, the tips of the staple legs should just about touch one another. The length of leg region 306 between the crown 301 and the deformation zone 305 should be matched to the requirements set by the combination of the thickness of the material being stapled and the compression of this material that is desired. The length of leg region 307 between the deformation zone 305 and the leg end 308 should be selected such that the separation of the leg ends 308 of the deformed staple is minimized without interference between the leg ends 308 occurring as the staple is deformed during installation. A comparison of FIG. 2 and FIG. 4 reveals that material stapled with the staple 300 of FIG. 3 will be less distorted and under more uniform compression than occurs with B-shaped staples. In FIG. 5, exemplary cross sections (not shown to the scale of FIG. 3) are shown for the legs 302 of the staple 300 of FIG. 3. In FIG. 5(a), a cross section for regions of the staple legs 302 outside the deformation zone 305 is shown. In FIG. 5(b) and (c) , two different possible cross sections for the staple leg cross section in the deformation zone 305 are shown. The values of I for the staple leg in deformation zones with the cross sections shown in FIG. 5(b) or (c) for bending into direction 304 are less than if they had the cross section of FIG. 5(a) . In FIG. 6, a double staggered staple line 600 formed from inventive staples 300 of FIG. 4 is shown, each row being offset with respect to the other row. Surgeons make use of double staggered staple lines, e.g., to compress tissue for hemostasis at the cut end of an organ or to perform an anastomosis. The present staples thus have application in hemostasis and anastomosis, for example. In FIG. 7, a cross section is shown of an anvil 700 for use with the staple of FIG. 3 to produce the deformed staple of FIG. 4. Channels 701 formed in the anvil 700 direct bending and deformation of staple legs 302 when staple 300 is forced against anvil 700 and the legs 302 encounter the anvil 700. Anvil 700 is stationary as the staple 300 is forced against it. In FIG. 8, an anvil 800 alternative to that of FIG. 7 for use with the staple 300 of FIG. 3 is shown. The legs 302 of the staple 300 encounter channels 801 of anvil 800 after penetrating through the material being stapled (not shown in FIG. 8) . Anvil 800 moves towards the staple 300 as the staple 300 is forced against the anvil 800. This motion of the anvil may be accomplished using means well known to the art. The motion of the anvil minimizes distortion of the material being stapled by the staple legs 302 as they bend and deform. It should be noted that the legs 302 after the staple 300 is deformed, as shown in FIG. 4, do not conform to the shape of the channel 701. Rather, the ends 308 of legs 302 follow the shape of the channels 701 until the leg regions 306 and 307 are bent at angles (preferably, at right angles) to one another. The stapler may include a stop (702, 802) to prevent staple bending beyond the desired amount, although such a stop is not required for the installation of a staple. An exemplary stop (702, 802) is shown, but other techniques using means well known in the art can be employed to prevent the stapler jaws from closing too much so that staples are deformed beyond desired points. Although stapler jaws are usually parallel to each other when the thickness of the material being stapled is uniform, material thickness sometimes varies over a length where a stapler line is to be inserted. In FIG. 9, an alternative staple jaws arrangement 900 is shown which includes two stapler jaws 901 and 902 (jaw 902 functions as an anvil) . This embodiment can -be used if the thickness of the material being stapled varies over the length of a line of staples that the surgeon wishes to insert. In order to maximize the benefits of the present invention and to achieve a good result, the upper jaw 901 is slanted with respect to the lower jaw 902, as shown. As a result, the separation of the stapler jaws 901 and 902 varies in correspondence with the variation in the thickness of the material (not shown in FIG. 9) being stapled. The individual staples used with the arrangement of FIG. 9 would have leg deformation zones located differently with respect to each other in order to accommodate the different thicknesses of the material being stapled. Specifically, it can be seen from FIG. 9 that the staple contacting channel 903 should have shorter leg lengths between its leg deformation zones and the staple crown than should the staple contacting channel 904. Additionally, the leg lengths of the staple used at channel 903 may be less than the leg lengths of the staple used at channel 904. It is possible for the staples to be manufactured with uniform cross section and material properties, and for the deformation zones to be formed by the surgeon by modifying the staples just prior to use so that they correspond to the requirements of the material being stapled. For example, the surgeon could notch or file the staple legs to create the deformation zones, and/or cut the staple legs to desired lengths. Devices which can be used for such purposes can use means well .known in the art. Such an approach would reduce the size of staple inventory requirements. FIG. 10 shows a loading strip 1001 carrying prior art staples 100. The loading strip 1001 can be place into a device (not shown in FIG. 10) which forms deformation zones where they are desired, and which also cuts the staple legs 102 to the desired lengths. Devices which can be used for such purposes can utilize means well known in the art. The loading strip 1001 would be inserted into a suitable stapler (not shown in FIG. 10) prior to insertion of the staples 100. FIG. 11 shows a still further embodiment of the invention wherein deformation zones are created as staples are inserted rather than prior to the use of the staples. The arrangement of FIG. 11 shows stapler jaws 1102, 1103 with a staple 1110 located therebetween. (Stapler jaw 1103 functions as an anvil.) Two bars 1101 are employed to form the deformation zones. The bars may be attached to the lower jaw 1103 or the upper jaw 1102. The specific technique of attaching the bars is not shown in FIG. 1 for purposes of clarity and is not material to the operation of the present invention, however means well known to the art can be used for such purpose. When the jaws 1102 and 1103 are brought towards each other, the staple 1100 will encounter the bars and bend and deform around the bars 1101. As seen in FIG. 12, the staple legs 1111 will deform so that leg portions 1106 and 1107 are at angles (preferably, at right angles) to each other, just as in embodiments where deformations zones are formed prior to staple insertion. Preferably, the anvil moves after the staple legs pass partly or completely through the material being stapled ' . Af er the staple has been deformed, the bars may move aside so that the stapler can be easily removed, or the stapler may be set up so that the stapler can slide in a direction out of the plane of FIG. 12 to disengage from the staple. Means to accomplish such disengagement are not shown, but means well known to the art can be used for such purpose. FIG. 13 shows a side view in cross section of another embodiment, including staple 10 as installed into tissue 12. The legs 26 of the staple 10 each include an upper deformation zone 18 surrounded by a first section 16 and a second section 20, and a lower deformation zone 24 surrounded by a third section 22 and the second section 20. The staple 10 includes a crown 14. During staple 10 insertion by a stapler (not shown) , the tips 23 of the legs 26 penetrate through the tissue 12 being stapled and encounter the stapler anvil (not shown) , which causes third sections 22 to rotate inwardly as the legs 26 bend and deform at the lower deformation zones 24. This causes second sections 20 and third sections 22 to assume an angle with respect to each other, e.g., to become substantially perpendicular to one another. As the stapler continues to push the staple 10 against the anvil, the legs 26 also bend inwardly and deform at the upper deformation regions 18, so that second sections 20 rotate with respect to first sections 16 and assume angles with respect to the first sections, e.g., substantially right angles. Preferably, the legs 26 bend initially at the lower deformation zones 24, and the lower deformation zones have more of a tendency to bend than the upper ones. When the staple installation process is complete and the legs 26 have deformed, third sections 22 penetrate into the tissue 12, as shown in FIG. 13. Of course, the amount of penetration into the tissue 12 depends upon the location of the lower deformation zones 24 with respect to the tips 23 of the legs 26. Ideally, the upper deformation zones should be located such that the lower deformation zones 24 nearly touch after full deformation. This will prevent tissue from bulging out between staple legs 26. It is noted that the area occupied by each staple is uniformly compressed. Thus, the entire stapled area can be viewed as having been divided into a plurality of areas, each of which is uniformly compressed. FIG. 14 shows the inventive staple 10 prior to installation into tissue 12. Staple 10 is a U-shaped before deformation, and includes an upper deformation zone 18 and a lower deformation zone 24 on each leg 26. Deformation zones 18 and 24 can be formed by reducing the sections of the legs 26 of the staple 10 or by other techniques, described herein. By having three different sections 16, 20 and 22 in each leg 26, the third sections 22 can be used to effect a small penetrations of tissue 12, i.e., produce a small and controlled amount of tissue damage so as to thereby stimulate formation of a small amount of scar tissue (not shown) , and the second section 20 and first sections 16 can be used to achieve uniform compression of tissue 12. FIG. 15 shows a prior art B-shaped staple 28 installed into tissue 38. There is a region 36 under the ends 34 of the legs 32 void of tissue, and scar tissue must form in this void region if it is to be filled. It is important to also note that the separation of the legs 32 from the crown 30 of the staple 28 is not uniform over the length of the legs, so that compression of the tissue 38 by the legs is not uniform. For such reasons, it is sometimes difficult to achieve hemostasis and allow proper nutrition of stapled tissues when using B-shaped staples. It is also a disadvantage of B-shaped staples that the ends 34 of the legs 32 penetrate deeply into the stapled tissues and twist around as the legs are deformed, so that substantial damage can be caused during staple installation with the result that excessive amounts of scar tissue forms with the possibility of strictures developing, and that bleeding can result from perforated blood vessels. Additionally, healing times may be extended. For purposes of explanation, as shown in FIG. 16, it is necessary to distinguish between the "inside" 401 of staple legs 26 and the "outside" 402 of staple legs 26. Concerning notches on the outside of the staple legs, FIG. 16 shows two such notches, one notch on each leg 26 used to form the upper deformation zones 18. Lower deformation zones may or may not be used and, if used, are not shown for purposes of clarity, but this discussion is applicable to lower deformation zones also. Notches cannot be excessively "sharp" or else the staple will fail, i.e., break or fracture, when the leg sections 16 and 20 are rotated with respect to each other or subsequently. In order to have acceptable notches formed on the outside of legs 26, the radius at the juncture where the sides of the notch meet must not be so small that the material of which the staple is formed, e. g., a metal such as a stainless steel or titanium, breaks, cracks or fractures during deformation of the leg at the deformation zone in question. It has been found that notches result in a so-called stress concentration, i.e., a localized stress which is considerably greater than the average stress in the section. While localized yielding for ductile staple materials can minimize the effects of stress concentration, staples in surgery are in a critical application where staple failure cannot be tolerated because the danger to the health and well-being of the patient. A tendency for the staple to fail due to the stress concentration that occurs at the juncture of a sharp notch formed on the outside of a leg when bending is unacceptable, and therefore a minimum radius must exist at the juncture of the notch. Such a minimum radius (fillet) should be at least 3/1000 of an inch. It is also preferable to manufacture staples with notches having a fillet of at least 3/1000 of an inch on the inside of the leg, rather than a sharp notch. FIG. 17 shows an expanded view of an upper deformation zone 18 in leg 26 in the form of a notch with a fillet 40 located at the juncture of the sides 42 of the notch. R is the radius of the fillet, and R is equal to or greater than 3/1000 of an inch in order to minimize the possibility of breakage or fracture of the staple leg upon bending during staple installation and to provide acceptable reliability, i.e., to avoid subsequent breakage of the leg after installation. While the above describes the preferred embodiment of the invention, it is understood that various modifications and or additions will be apparent to those of ordinary skill in the art. For example, the staples may be used in applications other than surgery. Staples with more than two legs may be used, e.g., a leg located between two outer legs may be used, where this additional leg need not have any deformation zones. While the disclosure has mentioned the use of these staples in surgery, it is clear that such staples can find uses in other applications, e.g., where uniform compression of the material underlying the staple is useful or where perforation of the material would be harmful. While particular anvils have been shown, the anvil used with the inventive staple need not be one of the anvils shown but may be any means of deforming the legs towards each other to achieve the deformed shape desired and may include means for stopping staple deformation after a desired amount of deformation has occurred. Further, while staples with two legs have been described, it is obvious that the principles of the invention are applicable to staples having more than two legs, e.g., for applications where a larger area is intended to be compressed by each staple. Such modifications and/or additions which fall within the spirit and the scope of the invention are intended to be covered by the following claims.

Claims: IN THE CLAIMS ; 1. A stapling arrangement comprising: a staple, the staple including; a crown having a crown length; at least two legs, each leg having an end, each of said legs being substantially perpendicular to said crown, each of said legs including at least one deformation zone, each deformation zone being defined as a first portion of said staple leg that is more susceptible to bending than adjacent portions of said staple leg, each leg having a second portion adjacent to said deformation zone and located between said deformation zone and said end of said staple leg, and a third portion adjacent to said deformation zone and located between said deformation zone and said crown of said staple, each of said second and third portions having a length, the length of said second portion of a first leg of said at least two legs and the length of said second portion of a second leg of said at least two legs, when added together, equaling substantially the crown length of the crown of the staple; a staple pusher, for pushing said staple into tissue to be stapled, said staple pusher being arranged to provide a force on said crown of said staple; an anvil, the anvil including at least one channel arranged to make contact with said end of said legs and to deform the first portion of said first leg until the second portion of said first leg forms substantially a right angle with respect to the third portion of said first leg, and to deform the first portion of said second leg until the second portion of said second leg forms a substantially right angle with respect to the third portion of said second leg. 2. The staple of claim 1 wherein at least one of said at least two legs has its said at least one deformation zone formed by decreasing its moment of inertia. 3. The staple of claim 1 wherein at least one of said at least two legs has its said at least one deformation zone formed by decreasing its modulus of elasticity. 4. The staple of claim 1 wherein at least one of said at least two legs has its said at least one deformation zone formed by decreasing its moment of inertia and its modulus of elasticity. 5. The staple of claim 1 wherein at least one of said at least two legs has its said at least one deformation zone formed by decreasing the area of its cross section. 6. A method of inserting a surgical staple into tissue, the surgical staple comprising a crown having a length and at least two legs, each of said at least two legs including an end, each of said legs further including at least one deformation zone, each deforma¬ tion zone being defined as a first portion of said staple leg that is more susceptible to bending than adjacent portions of said staple leg, each leg having a second portion adjacent to said deformation zone and located between said deformation zone and said end of said staple leg, and a third portion adjacent to said deformation zone and located between said deformation zone and said crown of said staple, each of said second and third portions having a length, the length of said second portion of a first leg of said at least two legs and the length of said second portion of a second leg of said at least two legs, when added together, equaling substantially the crown length of the crown of the staple, the method comprising the steps of: positioning a staple pusher on a first side of tissue to be stapled; positioning an anvil on a second side of tissue to be stapled; forcing said staple pusher against said crown of said staple, thereby pushing said ends of said legs through said tissue to be stapled and forcing said ends of said legs of said staple against said anvil; and continuing to force said ends of said legs against said anvil until a substantially right angle is formed on said second side of said tissue between said second portion of said first leg and said third portion of said first leg and a substantially right angle is formed on said second side of said tissue between said second portion of said second leg and said third portion of said second leg and until said staple forms a substantially closed rectangle, which rectangle substantially encloses the tissue being stapled. 7. The method of claim 6 utilizing a plurality of staples and wherein at least two of said plurality of staples include corre¬ sponding leg portions which differ in length with respect to each other. 8. The method of claim 6 wherein at least two of said staples are inserted into said tissue by different amounts with respect to each other. 9. The staple of claim 1 wherein at least one of said deformation zones is elongated. 10. The staple of claim l wherein said legs each include only one deformation zone. 11. The staple of claim 1 wherein said end of each of said legs includes a point located off-center. 12. A staple comprising: a crown ; at least two legs, at least two of said at least two legs having an upper deformation zone and a lower deformation zone,- the lower deformation zone having more of a tendency to bend than the upper ones. 13. A method of stapling comprising the steps of: inserting a staple having at least two legs into tissue to be stapled; deforming a first section of at least one of said at least two legs to substantially a right angle with respect to a second section of said at least one of said at least two legs; deforming a third section of said at least one of said at least two legs to substantially a right angle with respect to said second section of said at least one of said at least two legs, whereby said third section becomes embedded into the tissue being stapled such that said second sections are brought in close proximity to one another to prevent tissue from bulging therebetween. 14. The method of claim 13 wherein said first section and said second section are separated by a deformation zone. 15. The method of claim 13 wherein said second section and said third section are separated by a deformation zone. 16. The method of claim 14 wherein said second section and said third section are separated by a deformation zone. 17. A surgical staple comprising: a crown; and at least two legs, at least one leg of said at least two legs including an inside and an outside, said at least one leg also including at least one deformation zone, said at least one deformation zone being formed by a notch with a fillet with a minimum radius of 3/1000 of an inch. 18. A method of attaching a surface of a first tissue to a surface of a second tissue over a predetermined first area comprising the steps of: placing said first surface in contact with said second surface; and uniformly compressing a plurality of second areas of tissue within said first area. 19. The method of claim 18 wherein said uniformed compression is achieved by inserting a plurality of staples of said tissue. 20. The stapling arrangement according to claim 1 further comprising means for inhibiting further bending of said first and second legs after said right angle is formed in each of said at least two legs. 21. The method of claim 6 further comprising the step of: preventing the further deformation of staples after substantially right angles are formed in said first leg and said second leg. 22. A surgical staple comprising: a crown; and at least two legs, at least one leg of said at least two legs including at least one deformation zone, said at least one deformation zone not being formed by a sharp notch. 23. The staple according to claim 22 wherein said deformation zone is formed by a notch with a filet with a minimum radius of 3/1000 of an inch. 24. Apparatus for effectuating hemostasis in tissue comprising: means for inserting a plurality of staples, into said tissue; and means for deforming each of said staples to achieve uniform tissue compression.

Inventors: COOK MELVIN S, COOK, MELVIN, S.
Applicants: COOK MELVIN S, COOK, MELVIN, S.
Application year: 1994
Main classification: A61B17
IPC codes: A61B17